This invention relates generally to hollow metal golf club heads (sometimes referred to as metal woods) and more particularly concerns a hollow reinforced metal golf club head.
Hollow metal golf club heads in the shape of a golf driver are well known in the art and have been described in the prior art as early as 1928. Tobia U.S. Pat. No. 1,658,581. In recent years with the advent of improved materials and investment casting methods, metal drivers have become well accepted by golfers. Because metal drivers can be constructed with hollow interiors, the peripheral weighting of the metal driver head can be adjusted to provide significant advantages to the golfer in terms of location and size of the sweet spot of the club face.
In constructing hollow metal drivers, it is generally desirable to distribute the weight so that the club is balanced. A club head is balanced when the center of gravity is located on a line defined by the intersection of two perpendicular planes which both pass through the geometric center of the striking face of the club head. One of the planes is parallel to the sole of the club head, and the other plane is perpendicular to the sole of the club head. The second goal after balance is to distribute as much of the weight as possible about the periphery of the metal driver while maintaining the location of the center of gravity. Consequently, it is often necessary to reinforce the striking face of the metal driver, and the prior art shows numerous methods for reinforcing the striking face.
Zebelean, U.S. Pat. No. 4,432,549 discloses a hollow metal driver with a wedge shaped reinforcing rib extending between the striking face and the top of the club head which top appears to be of uniform thickness or to have a uniform taper from front to back. Allen, U.S. Pat. No. 4,930,781 shows a metal driver with a honeycomb matrix attached to the striking face to provide reinforcement for the striking face. Sugioka et al., U.S. Pat. No. 4,602,787 discloses a metal driver with two reinforcing ribs which connect the sole of the club to the striking face. Soda, U.S. Pat. No. 5,000,454 discloses a metal drive having a weight member of circular configuration with a pillar behind the striking face so that the load experienced by the striking face is transmitted by means of the pillar to the back side of the hollow club head. Kobayashi, U.S. Pat. No. 4,489,945 discloses a hollow metal driver in which the striking face is thicker near the sole plate than it is in the center or above. Thomson, U.S. Pat. No. 4,313,607 discloses a metal driver which has a reinforcing strut extending between the striking face and the back side for reinforcing the striking face. Additionally, the striking face has vertical ribs extending along a portion of the striking face but terminating short of the top side or the sole plate.
Tests of hollow metal metal drivers indicate that on impact, some of the energy of the impact is absorbed (and therefore lost) by deformation of the sole and top side of the club head. The result of such deformation is a loss of energy transfer to the ball and therefore loss of initial ball velocity and of distance. The prior art clubs have not addressed that deformation and loss of energy transfer in an integrated fashion focusing instead on reinforcing the striking face.